The process of this invention relates to printing designs, patterns, decorations, symbols, words, and the like of various colors on solid molded polymeric articles made from urea formaldehyde resin or melamine formaldehyde resin.
Printing color designs including decorations, symbols and words on materials can in most cases be considered as a form of localized dyeing. Printing of natural and synthetic materials like wool, cellulosic polyester blends, nylon, polyacrylonitrile and polyethylene can be accomplished by aqueous dyeing with aqueous dye solutions, dispersions, or pastes or by sublimation dyeing or by pad dyeing. Depending on the material to be printed, many types of dyes have been used in printing. These dyes include vat dyes, leuco esters of vat dyes, azoic colors, acid and direct dyes, acetate dyes, basic and mordant colors, disperse dyes and fiber reactive dyes.
Recently the use of sublimation transfer printing methods have become popular in the art for printing textiles. Generally, these methods involve printing an inert support (e.g., paper) with one or more sublimable dyestuffs usually with a cellulosic or similar binder and placing the printed support against the textile, and applying heat to cause the dyestuffs to vaporize and penetrate the textile. The sublimation transfer printing method has been used for textile materials such as wool, polyamide, polyester, polyacrylonitrile, and cellulose di- or triacetate fabrics. These fabrics are dry printed with vapors of a monoazo or anthraquinone disperse dye having a sublimation temperature less then 200.degree. C.
A recent observation was made in U.S. Pat. No. 3,877,964 (Orman) that general sublimation transfer printing methods are not generally effective for decorating some solid polymeric articles. In this patent it was discovered that in order to print or decorate an acrylic sheet the sheet had to be formed by polymerizing the continuous phase of an emulsion having an aqueous disperse phase and a continuous phase of acrylic monomer to form a water-filled cellular material, then the water had to be removed from at least a part of the surface of the material. This cellular material could be printed or decorated by heating a transfer print with sublimable dyes adjacent said part of the surface to a temperature above the sublimation temperature of the dyes so as to vaporize and transfer the dyes to said surface.
Solid molded polymeric substances made of urea formaldehyde resin or melamine formaldehyde resin are difficult to print or decorate. A recent development in the art of dyeing has been disclosed in U.S. Pat. No. 4,009,995 (Dressler). This development is the dyeing of molded synthetic plastic articles containing urea formaldehyde resin or melamine formaldehyde resin. The articles are treated in an aqueous dye bath containing 0.005 to 5.0 weight percent of a dichlorotriazinyl dye or a premetallized dye at a temperature in the range of 50.degree. to 100.degree. C.
Monochlorotriazinyl and dichlorotriazinyl dyes, which are reactive dyes, have been used to print on cellulosic fibers. In direct printing processes, these reactive dyes are often printed on the cellulosic fibers as a thickened aqueous solution containing urea and sodium carbonate or bicarbonate. The printed cellulosic fabric is dried, and the dye is fixed by steaming or baking.
We have found that sublimation transferring dyeing methods are not generally effective for printing or decorating solid molded polymeric articles made predominantly from urea formaldehyde resin or melamine formaldehyde resin. We have also found that even though the dichlorotriazinyl dyes are useful in dyeing plastic articles from a dye bath dichlorotriazinyl dyes do not sublime or vaporize to an acceptable extent to be used in a sublimation transfer printing process for solid molded polymeric articles made from urea formaldehyde resin or melamine formaldehyde resin.
It is an object of this invention to provide a process to print on solid molded polymeric articles made of urea formaldehyde resin or melamine formaldehyde resin to yield a printed or decorated article with good color fastness.